Sound field adjustment filter, sound field adjustment apparatus and sound field adjustment method

A sound field adjustment method for imparting desired sound field characteristics to acoustic signals outputted to a pair of speakers provided with a pair of left and right stereo channels comprising:

• sound field generating step, provided with a plurality of filter circuits with particular pass characteristics which respectively receive said acoustic signals of both channels, divide a predetermined frequency band of the acoustic signals into a plurality of frequency bands and individually adjust time delay and level of each divided frequency band, said sound field generating step comprising synthesizing the filter circuits to configure desired impulse responses in the entire frequency bands of the acoustic signals so as to generate sound field adjustment signals corresponding to the left and right channels, outputting the generated sound field adjustment signals respectively to other channel with each other, and allowing a listener to perceive virtual speakers whose opening angle between each other is changed with respect to said pair of speakers to thereby approximating the interaural correlation coefficient for perceiving a listening feeling in accordance with a preference;
• delaying step of adding delay time of said sound field generating process to the acoustic signals in the left and right channels;
• and
• signal operation step of adding said sound field adjustment signals with time delay to said acoustic signals in the left and right channels.